Most animal cells have the ability to secrete extracellular vesicles of intracellular origin with various sizes and components, and these extracellular vesicles are found in all biological fluids including blood, urine, saliva, and cell culture fluids (Loyer X, Vion A C, Tedgui A, Boulanger C M, Microvesicles as cell-cell messengers in cardiovascular diseases, Circ Res 2014; 114: 345-53, Ohno S, Ishikawa A, Kuroda M. Roles of exosomes and microvesicles in disease pathogenesis. Adv Drug Deliv Rev 2013; 65: 398-401).
Extracellular vesicle is a membrane vesicle having a diameter of about 20 nm to about 5 μm, and is heterogeneous in its size and composition. They are classified into multiple different types including exosomes, ectosomes, microvesicles, microparticles, apoptotic bodies, etc.
Extracellular vesicle reflects the state of the secreting cells (donor cells), exhibits various biological activities depending on the type of the secreting cells, and plays an important role in intercellular interactions by transferring genetic materials and proteins between cells.
Melanin is a phenol-based biopolymer in the form of a complex of black pigment and protein. It is found in browning, which occurs when a cut surface of an apple, a potato, or a banana is exposed to air, or in the outer feathers, skin, head, eyes, etc. of animals. When melanin is overproduced, it is deposited on the skin to form spots and freckles, promote skin aging, and may even cause skin cancer.
Melanocytes in the human body are cells synthesizing melanin as a part of defense mechanism against ultraviolet rays from the outside. They prevent apoptosis of the skin due to ultraviolet rays. When the skin is exposed to ultraviolet rays from the outside, melanocytes among skin tissue cells react with ultraviolet rays to synthesize melanin.
The mechanism of the synthesis of melanin by ultraviolet rays is as follows: Melanin stimulating hormone (MSH) is secreted due to ultraviolet rays and MSH responds to the receptor MC1R to increase cAMP in melanocytes, which induces the reaction of genes for melanin synthesis, resulting in the synthesis of melanin. The synthesized melanin is secreted out of the melanocytes to protect the skin from ultraviolet rays. Proteins involved in the biosynthesis of melanin include mitf, tyr, trp1, and trp2.
However, there has been no report on the relationship between the amount of secretion of exosomes secreted from melanocytes and apoptosis of melanocytes. Prior art relating to a method for screening for materials having whitening activities is described in Korean Patent No. 10-0840144.